Rotary screen printing machines are well known and typically include a frame, backing means supported by the frame, and at least one, and usually a plurality, or rotary screen assemblies which are carried by the frame in adjustable relationship with respect to the backing means. Typically, each rotary screen assembly includes an inner elongated member, an outer hollow patterned screen supported about the inner elongated support member for rotation thereabout, and an elongated applicator, such as a conventional squeegee, which is supported on the elongated support member and engages the inner surface of the screen to press the coloring paste or ink through the perforated pattern thereof as the fabric being printed is passed between the respective hollow screen and the backing means. In a rotary type screen printing machine, the backing means comprises a large drum and the plurality of rotary screen assemblies are supported circumferentially thereabout. In a flat bed screen printing machine, it is normal practice to provide the rotary screen assemblies in a common plane with each screen assembly being provided with a cooperating back-up roller associated therewith.
Since the pressure of the applicator (i.e., squeegee) plays such an important role in controlling the quality of the printing, various prior art techniques have been suggested for permitting adjustment of the squeegee with respect to the inner surface of the screen. For example, U.S. Pat. Nos. 3,196,784; 3,216,349, 3,566,784; 3,592,132; and 3,596,595 disclose magnetic attraction techniques for selectively drawing the squeegee into contact with the interior surface of the screen. As another approach, U.S. Pat. Nos. 2,928,340 and 3,186,339 disclose the use of fluid actuated pistons which are connected to the squeegee to be controlled thereby. As another approach, U.S. Pat. Nos. 2,292,602; 2,571,064; and 3,229,624 employ springs to bias the squeegee against the interior surface of the screen.
More recently, it has been suggested to employ an elongated inflatable tube to control the pressure of the squeegee against the inner surface of the printing screen. In this prior art device, an inflatable tube corresponding to the length of the printing screen is supported on the inner support shaft of the rotary screen assembly and located behind the squeegee member. By controlling the inflation of the tube, the amount of squeegee pressure against the inner surface of the screen may be varied. As will be pointed out below, an important aspect of the instant invention is to provide an improvement over this type of squeegee pressure adjustment technique.
It has also been appreciated with respect to the above-described type of screen printing machine that it is desirable to provide an adjusting mechanism for varying the angle at which the squeegee engages the inner surface of the screen. In prior art machines, however, such adjustment can only be accomplished by removing the hollow screen so as to expose the squeegee and the mechanism for varying the angular position thereof. In addition, such adjusting mechanism of the prior art machines has been rather complex.
Similarly, prior art machines have been provided with adjusting mechanisms for varying the position of the screen of each rotary screen assembly with respect to its associated backing member. Unfortunately, the various techniques provided in the prior art machines are rather complex and no simple mechanism has been developed to provide all the desired degrees of motion of the screen. As noted below, a section aspect of the invention is to provide a screen printing machine with improved mechanisms for achieving the various desirable movements of the screens with respect to their associated backing member.